1. Field of the Invention
This invention relates to an apparatus and method for examining key plates, and, in particular, to an apparatus and method for examining key plates by comparing the form of a key plate being examined with the form of a reference key plate and the specification values for determination.
2. Description of the Related Art
It is known to represent the form of a key plate, such as an ignition key of a car, the undulation dimensions of mountain-and-valley-like irregularities of the key plate, and their combination as a key code consisting of a plurality of digits. Car manufacturers have prepared and managed the key plates for each car based on the key codes. On the other hand, key manufacturers and car manufacturers need to display key codes, which indicates form information of key plates, on the key plates for preparing spare keys, etc., while preventing outsiders from easily reproducing the key plates. Therefore, in fact, the key numbers (symbols corresponding to the key codes on a one-to-one basis) prepared based on the key code collation tables owned by the key manufactures and the car manufacturers are represented on the key plates.
To examine whether or not each key plate thus prepared and managed has a combination of irregularities as its key code and whether or not the irregular form is machined within the tolerance of the form specification values, for example, the dimensions of the key plate are directly measured with measuring instruments, such as slide calipers and micrometers, or the key plate is projected by a projector and the key plate dimensions are calculated. The measured dimensions are then collated with the dimensions on a work drawing and form information of the key code retrieved according to the key number displayed on the key plate in order to examine the key plate form. For example, disclosed in Japanese Patent Publication No. Sho 58-19832 is a key code display device which brings a plurality of styli into contact with the irregularities of a key plate, calculates a key code in response to the displacement amount of the styli, and displays the key code.
Thus, the key plate dimensions and key code detected in contact or non-contact with a key plate are collated with an enormous amount of key information of reference key plates listed in collation tables.
However, the conventional key plate form examination requires comparison or collation of form information, such as the dimensions and combination of irregularities of the key plate, measured with form information of the reference key plates provided from key code collation tables and work drawings. As a result, it takes a long time to examine the key plates and an error is prone to occur in comparison or collation because of the large amount of key plates which differ slightly in form.
When the key plate form is measured with contact measuring instruments such as slide calipers and micrometers or styli, it is difficult to eliminate completely measurement errors. As a result, a proper determination as to whether or not the measured dimensions match the dimension specification values cannot be made.